What's the problem this feature will solve?

pip freeze --find-links=somewhere will simply output -f somewhere at the beginning of the output:

Except for history (this option exists since the freeze command and 3d32c19), there is no reason to special case it and not allow --index-url, --pre and all the other options allowed in a requirements file.

Describe the solution you'd like

Deprecate and remove it.

Alternative Solutions

Keep it.

Additional context

Deprecating it would ease the transition for #7157